Known processes of constructing printed circuit board layers include the use of photo-resist material and etching to produce traces and other features on layers which are then built up to produce a finished printed circuit board. During production of each layer it is known to use films of a diazo material with patterns formed on them to expose the photo-resist on printed circuit board layers. In that process, the film is placed on top of the surface to be patterned, and a light source is activated to transfer the pattern from the film to a photo-resist layer coated on the circuit board layer. After exposure, the photo-resist is developed and removed and the circuit board layer is metallized as desired.
That technique does, however, include problems. In particular, the films used to transfer the patterns to the photo-resist layer lack dimensional stability which decreases the accuracy of registration between layers of a multi-layer printed circuit board assembly. Registration accuracy is compromised because the films, typically of thermoplastic materials, have dimensions which change in response to aging and changes in temperature and/or humidity. In addition, the films are also not particularly durable and they may be rendered useless if the pattern on them is damaged during handling. Multi-layer stacked printed circuit boards with two-sided layers, however, require high levels of accuracy in registration because errors in registration compound as more layers are laminated together to produce a desired multi-layer PCB. As a result, the production of multi-layer stacked PCB's has been limited by registration problems.